Polyester sheath-core conjugate filaments

ABSTRACT

Sheath/core conjugate filaments which combine the tensile properties of poly(ethylene terephthalate) as core with the surface properties of a copolyester of ethylene terephthalate/polyoxyethylene terephthalate as sheath.

United States Patent Inventors John Raymond Brayford;

Ian Stuart Fisher; Michael Mundie Robertson, all of l-larrogate, EnglandPOLYESTER SHEATH-CORE CONJUGATE FILAMENTS 20 Claims, No Drawings 11.5.CI 161/175, 264/171 int. Cl D0ld 5/28 Field of Search 161/172, 175;260/860; 264/171 [56] References Cited UNITED STATES PATENTS 2,987,7976/1961 Breen 161/173 3,329,557 7/1967 Magat eta]. .1 260/873 X OTHERREFERENCES D. Coleman, Block Copolymers: Copolymerization of EthyleneTerephthalate and Polyoxyethylene Glycols Jour. Polymer Science, Vol.XIV, pp. 15- 27 (1954).

Primary Examiner- Robert F. Burnett Assistant Examiner- Raymond O.Linker, Jr. Attorney-Cushman, Darby & Cushman ABSTRACT: Sheath/coreconjugate filaments which combine the tensile properties ofpoly(ethylene terephthalate) as core with the surface properties of a copolyester of ethylene terephthalate/polyoxyethylene terephthalate assheath.

POLYESTER SHEATl-l-CORE CONJUGATE FILAMENTS The present inventionrelates to the preparation of conjugate polyester fibers having goodsoil-release properties and good antistatic properties, these propertiesbeing permanent under very stringent treatment conditions.

According to the present invention we provide a process for thepreparation of a conjugate polyester filament by the extrusion insheath/core relationship of (a) a stream of molten, fiber-forming,linear polyester or copolyester based on a simple glycol, or of molten,fiber-forming copolyester in the molecular chain of which there are, inaddition to units based on a simple glycol, poly(alkyleneoxide)-containing units in proportion such as would result from thereaction of less than parts by weight of poly(alkylene oxide) per 100parts by weight of the final copolyester, and (b) a stream offiber-forming copolyester, or a fiber-forming admixture of copolyester,having structural units containing poly(alkylene oxide) radicals, theproportion of the structural units containing poly(alkylene oxide)radicals being such as would result from the reaction of not less than 5and not more than 60 parts by weight of poly(alkylene oxide) of averagemolecular weight at least 500, per 100 parts by weight of the finalcopolyester or copolyester admixture, (a) being the core and (b) beingthe sheath, allowing the composite stream to solidify to form a filamentand subsequently cold drawing.

According to a preferment of our invention, in a fiber-formingcopolyester used for the core the proportion of units which arepoly(alkylene oxide) containing should not exceed that corresponding tothat which would result from the reaction of 3 parts by weight ofpoly(alkylene oxide) per 100 parts by weight of the final copolyester.

Our invention also includes sheath-core conjugate filaments madeaccording to the process of our invention.

By the term "simple glycol" we mean a glycol which is not a polyglycol.Examples of simple glycols are those having the general formulaHO(CH,),,OH, wherein n is not less than 2 and not greater than 10, andlz4-(hydroxymethyl) cyclohexane. in the term simple glycol we alsoinclude more than one simple glycol.

Preferably the proportion of structural units of the component (b) whichare derived from poly(alkylene oxide) does not exceed that which wouldresult from the reaction of 40 parts by weight of poly(alkylene oxide)in the formation of 100 parts by weight of the final copolyester orcopolyester admixture.

In order to avoid spun yarn stickiness, which leads to difficulty inunwinding packages of spun yarn during drawing, it is preferable thatthe proportion of'structural units ofthe components (b) which arederived from poly(alkylene oxide) is not excessive. This proportion maybe greater in the case of a higher molecular weight poly(alkylene oxide)than in the case of a lower molecular weight poly(alkylene oxide). Thisrelationship is illustrated in the examples given hereinafter.

By the term admixed copolyester" we mean a mixture containing acopolyester of which a proportion of its structural units containpoly(alkylene oxide) radicals; the admixed copolyester may be a mixtureof more than one copolyester; more than one copolyester present maycontain structural units based on poly(alkylene oxide). Thus it isnecessary that the component (b) should contain poly(alkylene oxide) ofaverage molecular weight of at least 500 in combined form equivalent toat least 5 and not in excess of 60 parts by weight of poly(alkyleneoxide) per 100 parts by weight of the component (b).

We have found particularly advantageous the use as component (b) of acopolyester or admixed copolyester which is fiber-forming and which hasan effective melting point not less than 200 C. These conditions favorsuccessful extrusion to form filaments and successful orientation bycold drawing. it is not, however, essential that the copolyestercontaining poly(alkylene oxide) units should in itself be fiber-formingwhen it is only a constituent of the fiber'forming component (b).

An advantage of the process of our invention is that by means of itfilaments may be produced having adequate tensile crease resistant andpleat retention properties for all normal fiber uses and at the sametime having good antistatic pro pcrties and having good soil-releaseproperties, these properties being permanent under very stringenttreatment conditions, and these fibers having excellent stabilitytowards the irradiation by ultraviolet radiation, and dyestuffsintroduced into such fibers having high light fastness.

Such an advantageous combination of properties cannot be obtained in,for example, a homofilament of a polyester or ensure a copolyester whichdoes not have poly(alkylene oxide) units in its molecule or ahomofilament which has a proportion of its structural units containingterephthalate) oxide) radicals such as would result from the reaction ofnot less than 5 28 parts by weight of poly(alkylene oxide) per pans byweight of the final copolyester.

Thus the filaments of our invention have in the sheath a greaterproportion of combined poly(alkylene oxide) than is found in the core.Preferably the proportion of combined poly(alkylene oxide) in the coreshould be less than that which would result from the reaction of 5 partsby weight of poly(alkylene oxide) per 100 parts by weight of the corematerial. There may advantageously be no poly(alkylene oxide) in thecore and we have found that all benefits of our invention are fullyrealized when the proportion of poly(alkylene oxide)- containing unitsis such as would result from the reaction of as much as 3 parts byweight of poly(alkylene oxide) per 100 parts by weight of the finalcopolyester.

The proportion of the conjugate filament cross section which is composedof the component (b) should be sufficient to provide an entire sheathabout the core, on the other hand such proportion should not be so greatthat the dye-fastness and light-resistance properties are adverselyaffected. After subjecting the sheath core filaments of our invention toa dyeing procedure, the resultant and exemplified may be reductioncleared, according to known technique and exemplified in the exampleshereinafter. This treatment results in removal of the dyestuff from thesheath of the filaments so that the lack of dye-fastne ss and the lackof light resistance normally associated with the presence of dyestuff inthe material ofwhich the sheath is composed is no longer a problem. Onthe otherhand, the presence of dyestuff in the core of the filamentsensures the desirable colored appearance of the filaments and thedyestuff in the core is fast and light resistant. Thus the proportion ofthe cross-sectional area being composed of com ponent (b) should be notless than 5 percent and not greater than 40 percent. Provided theserequirements are met, the filaments may be of concentric or eccentricconformation and of circular or noncircular cross section.

Any convenient method may be used for the formation of the conjugatestream of(a) in (b) examples of which are;

i. the combination in appropriate configuration of a polymer of type (a)with a polymer of type (b), by, for ex ample, the use of the apparatusdescribed in U.S. Pat. No. 3,457,342.

ii. the splitting of a stream of a molten polyester or copolyester oftype (a) into two streams, the incorporation into one stream of apoly(alkylene oxide) under such conditions that it reacts to form amodified copolyester and recombination of the two streams in sheath corerela' tionship with the modified stream as the sheath.

iii. the splitting of a stream of molten polyester or copolyester oftype (a) into two streams. the incorporation into one of the streams ofthe polyester of a copolyester of which a relatively high proportion ofthe structural units are poly(alkylene oxide)-containing units andrecombination of the two streams in sheath core relationship with themodified stream as the sheath. in this method, as opposed to method(ii), it is optional whether the conditions are or are not such thatreaction takes place between the components of the modified stream.

In each of the cases (i), (ii) and (iii) it is necessary that therequirements hereinbefore stated should be fulfilled, that is the coreshould either be of a polyester or of a copolyester of which theproportion of structural units which contain poly(alkylene oxide) isless than that which would result from the reaction of 5 parts byweight, and preferably no more than that which would result from thereaction of 3 parts by weight, of polyalkylene oxide per 100 parts byweight of final copolyester, and the sheath should contain at least thatproportion of units containing poly(alkylene oxide) radicalscorresponding to 5 parts of poly(alkylene oxide) per 100 parts by weightof sheath component, regardless of whether there is one molecularspecies containing poly(alkylene oxide) radicals, or more than onemolecular species containing poly(alkylene oxide) radicals, and alsoregardless of whether or not all molecular species present containpoly(alkylene oxide) radicals. The poly(alkylene oxide) having shouldpreferably be poly(ethylene) oxide or poly(propylene oxide), having anaverage molecular weight not less than 1,000 and not greater than20,000. Preferably the average molecular weight should be not greaterthan 6,000. The average molecular weight in question is that for adistribution of molecular weight of poly(alkylene oxide) asmanufactured.

Examples of suitable dicarboxylic acids on which the polyesters orcopolyesters of sheath of core may be based are terephthalic,naphthalene-2:6-dicarboxylic and 1:2-diphenoxyethane-4z4-dicarboxylicacids. Suitable second dicarboxylic acids for such copolyesters as havesuch, are, for example, adipic, isophthalic and sulfoisophthalic acids.A proportion or the whole of the units of which the polymer or polymerscomprising the component (b) is or are composed may differ from theunits of the polymer of component (a), for example, in respect of thedicarboxylic acid on which the units are based.

The most effective polyester for the core is poly(ethyleneterephthalate). It is most practicable for the sheath material to be ofa single copolyester of ethylene terephthalate having as other thanethylene terephthalate structural units only poly(oxyethylene)terephthalate units.

The filaments manufactured according to the process of our invention maybe produced by the use ofa multihole spinneret to form a yarn which maybe oriented by cold drawing according to methods known in the art.

Each of the components (a) and (b) may optionally contain additivescommonly present, and in the proportion commonly used, to producedesired effects, for example coloring materials, delustrants, dyeingadditives and stabilizers. Such effects may be confined to the sheath orto the core.

The filaments of our invention may be used in all textile uses, ascontinuous filament or staple fiber alone or in admixture with otherfilaments or fibers particularly where soil is a problem, and whereantisoiling and antistatic properties are important.

In order that the process of our invention may the more fully beunderstood, we give hereinafter examples of methods in which it may beput into practice.

In the following examples by Viscosity Ratio we mean the ratio 1; where'r is viscosity of the solution of polymer and 17 is the viscosity ofthe pure solvent. Determination of Viscosity Ratio was carried out at 25C. in orthochlorophenol at a concentration of 1 g. of polymer to 100 ml.ofsolvent.

EXAMPLE 1 A mixture of bis(B-hydroxyethyl) terephthalate, (1,070 parts),poly(ethylene oxide) of average molecular weight 4,000 (730 parts) andantimony trioxide (1.46 parts) was heated under an atmosphere ofnitrogen in a stainless steel autoclave to a temperature of 260 C. Thetemperature was maintained at 255-265 c. while the pressure was reducedto less than 0.2 mm. of mercury over a period of 1 hour andpolymerization was continued at 255-265 C. for a further 3 hours. Thepressure was then restored to atmospheric. Dry poly(ethyleneterephthalate) chip of Viscosity Ratio 1.81

(1,400 parts) and 2:4-dimethyl-6-a-methylcyclohexylphenol (40 pants) (asstabilizer) were added to the autoclave, the pressure reduced to 0.3 mm.of mercury and the temperature raised to 275 C. over a period of 1 hourwith continuous agitation. The resultant product was a polyester blendhaving Viscosity Ratio 2.06 and a crystalline melting point of 23 1 C.

A sheath-core yarn was spun by melt-spinning according to method (i)described hereinbefore, using the resultant polyester blend as thesheath component and poly(ethylene terephthalate) of Viscosity Ratio1.81 as the core and using a core to sheath ratio 2:1 by volume.Extruder temperatures of 275-285 C. and 260-270 C. were used for thecore and sheath respectively. The spun yarn had a denier of 350 andcomprised 36 filaments. The spun yarn was drawn over a pin at C. and aplate at 175 C. using a draw ratio of 3.22 to 1 giving a drawn yarnhaving tenacity 3.6 g. per denier, extension 31 percent and shrinkage5.6 percent.

Samples of the drawn yarn were knitted into hoselegs and subjected tothe following conditions of vat dyeing. A knitted sample was heated at60 C. with an aqueous solution of sodium hydroxide (25 g. per liter) andsodium hyposulfite Na,s,o (17.5 g. per liter) for 1 hour using aliquor-to-fabric ratio of 40:1. The fabric was then rinsed thoroughly inwater, dried, rinsed in distilled water containing potassium bromide(1.5 g. per liter), spin dried for 2 minutes and tumble dried at 60 C.The lengthwise electrical resistance of the fabric sample, 7 inches by1.5 inches and comprised of six fabric layers, was 3.0 X10 megohms,measured at 65 percent relative humidity. This may be compared with anidentical test carried out on fabric otherwise identical but composed ofpercent poly(ethylene terephthalate) yarn, both before and after thealkali treatment, for which the electrical resistance was greater than10 megohms in each case.

EXAMPLE 2 Poly(ethylene terephthalate) was prepared by polycondensationof bis(B-hydroxyethyl terephthalate) (2,000 parts) using antimonytrioxide as catalyst. Polycondensation was stopped when the desiredlevel of melt viscosity was reached (about 1,000 poises at 285 C.) asjudged by previous knowledge of the relationship between the meltviscosity and the power required to drive the agitator. Thepoly(ethylene terephthalate) product was mixed in the molten state at270 C. with poly(ethylene oxide) of average molecular weight 5,000 (500parts) and the reaction mixture was subjected to polycondensationconditions at 270 C. until the desired level of melt viscosity wasreached as judged by previous knowledge of the relationship between meltviscosity and power required to drive the agitator. The reaction productwas then a copolyester derived from 25 parts by weight of poly(ethyleneoxide) per 100 parts by weight of the final copolyester and was ofViscosity Ratio 2.01.

A 36-filament sheath-core yarn was spun according to method (i)described hereinbefore, the core being formed from poly(ethyleneterephthalate) of Viscosity Ratio 1.81 and the sheath being formed fromthe copolyester of which the preparation is described in this example.The ratio of the cross-sectional areas of core to sheath was 57:1. Theextrusion temperatures for core and for sheath were respectively 280 C.and 270 C. The spun yarn had denier 435. The spun yarn was drawn over apin at 85 C. and a plate at C. using a draw ratio of 3.65 to 1 to give adrawn yarn having tenacity 5.4 g. per denier and extension 14 percent.

Samples of the drawn yarn were knitted into hoselegs and subjected tothe following conditions of carrier dyeing. A knitted sample was addedto a solution of the sodium salt of methylene dinaphthalene sulfonicacid (0.01 g. per liter) in sufficient water to give 30:1 liquor tosample by weight and 30 percent acetic acid (4.8 ml. per liter) at 40 C.The dyestuff Color Index Disperse Yellow 39 (2 percent) by weight on theknitted sample was added to the liquid, which was raised to the boil. Tothe boiling liquid there was added sufficient 0,0-

dihydroxydiphenyl in the form of a strong aqueous solution so that thefinal solution contained 3.5 g. per liter. The solution was maintainedat the boil for a further 60 minutes. The fabric was then firstlyreduction cleared by treating in an aqueous bath of cetyl trimethylammonium bromide (0.28 g. per liter), a condensate of cetyl alcohol and22 mols per mol. of ethylene oxide (0.28 g. per liter), sodiumhyposulfite (2 g. per liter) and sodium hydroxide (2 g. per liter) at 50C. for 20 minutes and then soaped by treating in a bath of sodium oleylsulfate (1 g. per liter) and sodium carbonate (1 g. per liter) at 6570C.

.for 20 minutes. The fabric was then rinsed thoroughly in water, dried,rinsed in distilled water containing potassium bromide (1.5 g. perliter) spin dried for 2 minutes and tumble dried at 60 C. The lengthwiseelectrical resistance of the fabric sample, 7 inches by 1.5 inches andconsisting of six fabric layers, was 9 X 3 megohms, measured at 65percent relative humidity. This may be compared with the results of anidentical test carried out on fabric otherwise identical but composed of100 percent poly(ethylene terephthalate) yarn, for which the electricalresistance was greater than 10 megohms. The wettability and oildisplacement by water was greatly superior for the fabric derived fromthe sheath-core filaments of our invention as compared with that offilaments of 100 percent poly(ethylene terephthalate). Thus this exampledemonstrates that the improved properties conferred by our invention arenot destroyed by the hot alkaline conditions of dyeing and reductionclearings.

When poly(alkylene oxide) is present in a polyester as such, rather thanin the form of chain-linking units, the resultant antistatic effect ofthe polymer is not durable, that is it is removed by simple washing.

This distinction is illustrated by examples 3-5.

EXAMPLE 3 A sheath-core conjugate yarn of 36 filaments and 5 denier perfilament is spun and drawn according to the method described in example2. The core was poly(ethylene terephthalate) of Viscosity Ratio 1.81 andoccupied 85 percent of the cross-sectional area of the filament. Thesheath was a copoly(ethylene terephthalate) of Viscosity Ratio [.70containing units derived from poly(ethylene oxide) of average molecularweight 5,000 in quantity such as would result from the reaction of l5parts by weight per 100 parts by weight of the final copolyester.

EXAMPLE 4 Poly(ethylene terephthalate) of Viscosity Ratio 1.81 wasblended with poly(ethylene glycol) of average molecular weight 20,000 inan amount to give a resultant dispersion containing parts by weight ofthe poly(ethylene glycol) per 100 parts by weight of the total blend,the blending being carried out so that reaction did not occur to causeincorporation of the poly(ethylene glycol into the poly(ethyleneterephthalate) chains. The blend was melt spun and drawn in theconventional way according to example 2 to form yarn of 36 fi1aments and5 denier per filament.

EXAMPLE 5 The yarns from examples 3 and 4 were knitted to hoselegfabrics and then washed in a dilute detergent solution at 60 C. for 6minutes. The lengthwise electrical resistances of the washed fabricsamples were then measured at 65 percent relative humidity as describedin example 2. The washed fabric form example 4 had a resistance greaterthan l0 megohms (i.e. beyond the range of the instrument used) and alsoshowed a strong tendency to form static changes.

In contrast, the washed fabric from the yarn of our convention (example3) had a resistance of 7 X10 megohms and showed good resistance todeveloping a static charge.

EXAMPLE 6 A drawn sheath-core filament yarn of36 filaments and 4 denierper filament was prepared according to the method described in example 2the core being of poly(ethylene terephthalate) of Viscosity Ratio 1.81and occupying percent of the cross-sectional area of the filament andthe sheath being of a copolyethylene terephthalate such as would resultfrom the reaction of 18 parts by weight of poly(ethylene oxide) ofaverage molecular weight 5,000 per parts by weight of the finalcopolyester and of Viscosity Ratio 1.91.

EXAMPLE 7 Table l Tenacity g. per denier Number of hours of exposure ML50 100 SAMPLE Poly(ethylene terephthalate) control 4.2 3.8 3.6 3.5Conjugate filament yarn of example 6 3.9 3.5 3.1 3.1 Filament yarn ofexample 7 3.6 2.6 1.3 2.2

It can be seen that as regards retention of tenacity the yarn of example6 is almost as good as the poly(ethylene terephthalate while the yarn ofexample 7 consisting of a copoly(ethylene terephthalate) is inferior toboth the poly(ethylene terephthalate) yarn and to the conjugate yarn ofexample 6 according to our invention.

EXAMPLE 8 Comparison was made in respect of the drawing and dye fastnessproperties of the following three drawn yarns, all of which were of 36filaments and 4 denier per filament and differed in the followingrespects:

Sample (i) Filament yarn of poly(ethylene terephthalate) Sample (ii)Conjugate filament yarn of our invention and according to example 6.Sample (iii) Filament yarn of co(polyethylene terephthalate) accordingto example 7.

The yarns were knitted into hose leg fabrics and dyeings carried outseparately with each of the dyestuffs Color Index Disperse Blue 26,Color Index Disperse Blue 56, Color Index Color index Disperse Blue 122,using the dyeing conditions given in example 2.

It was found in all cases that sample (iii) dyed to a deeper shade thansamples (i) and (ii) but (iii) suffered from the grave disadvantage thatmuch of the dye could be removed from the fiber by simple treatmentssuch as solvent extraction, e.g. with methanol, or by reduction clearingas described in example 2. Such treatments led to a complete eliminationof, or a drastic reduction in, the depth of shade. Reduction clearingand soaping could not therefore be used and the dye fastness propertiesof sample (iii) compared with sample (i) were as given in table 2.

TABLE 2 Cross staining Rub fastness Light Dye Sample W 001 Nylon D1 yWet fastness (Cl Disperse Blue 26) Sample (iii).-. 2-3 '2 4 4 3-4 Sample(1) 4 4 5 5 4-5 (CI Disperse Blue 56) Sample (iii). 3 3 3-4 4 3 Sample(1) 5 4-5 4-5 5 4 (CI Disperse Blue 122) Sample (iii). 2-3 4 5 5 22-3Sample (1) 4-5 4-5 5 5 3-4 The fastness gradings in these tests wereobtained by the methods published by the Society of Dyers and Coloristsunder the title Standard Methods for the Determination of Color Fastnessof Textiles. The fastness gradings were determined by reference to theGeometric Grey Scales for assessing the results of fastness testing.

By contrasting, dyed samples of fabric (ii) could be reduction clearedand soaped as described in example 2 and suffered a relatively slightdecrease in shade. The dye fastness properties after these treatmentswere also superior to those of sample (iii) as shown in table 3.

EXAMPLES 10-15 TABLE 3 I Cross staining Rub fastness Light Dye SampleWool Nylon Dry Wet fastness (Cl Dispersc Blue 26) Sample (ii). 4 3-4 4-5 4-5 4-5 Sample (i) 4 4-5 5 5 4-5 (Ci Dispersc Blue 56). Sample (ii) 44-5 4 4 4 Sample (i) 5 4-5 4 4 4 (CI Disperse Blue 122) Sample (ii) 4-54-5 5 5 3-4 Sample (i) 4-5 4-5 5 5 3-4 EXAMPLE 9 about a core ofpoly(ethylene terephthalate) as used for the i. Poly(tetramethyleneterephthalate) of a Viscosity Ratio 2.18 was prepared by a conventionalmethod and was melt spun and drawn to form a yarn.

ii. Poly(ethylene terephthalate) of Viscosity Ratio 1.81 was melt spunand drawn to form a yarn.

iii. A copoly(ethylene terephthalate) containing units derived frompoly(ethylene oxide) of average molecular weight 5,000 in quantity suchas would result from the reaction of 18 parts by weight per 100 parts byweight of the final copolyester and having Viscosity Ratio 1.91 wasprepared according to the method of example 2.

iv. Conjugate filaments were spun from the polyester of (i) as core and(iii) as sheath, the core occupying 85 percent of the cross-sectionalarea of the filament and the filaments drawn.

v. Conjugate filaments were spun from (ii) as core and (iii) as sheath,the core occupying 85 percent of the cross-sectional area of thefilament for 30 seconds and after heat setting of 140 C. for 30 seconds.The values for percentage tensile recovery are given in table 4.

control. The proportion of the cross sectional area of the conjugatefilaments occupied by the core was percent in each case. The conjugateyarns and the poly(ethylene and terephthalate) control yarn were knittedinto hose leg fabrics and subjected to a soiling treatment consisting inwashing under standard conditions in aqueous detergent solution in thepresence of standard samples of soiled flannellette. in table 5 aregiven in column 2 the parts by weight of poly(ethylene oxide) used inthe preparation of parts by weight of the sheath copolyester, in column3 the value for reflectance of the fabric before the soiling test, incolumn 4 the value for reflectance of the yarn after the soiling testand in column 5 the difference in values given in columns 3 and 4.

TAfiLE 5 Parts poly- Reflectance values (ethylene oxide) in 100 pts. oiBefore After Ditiercopolyester in soiling, soiling. once, Example sheathA 13 A- ll 0 S0 00 20 5 84 60 5 12 8O 76 4 17 78 74 4 21 T8 75 3 25 7977 2 Percent oil retained:

Percent oil remaining on conjugate filament sample) X 100 Percent oilremaining on poly (ethylene terephthalate) filament sample.

The results are given in table 6, in which the parts of poly(ethyleneoxide) has the same significance as in table 5.

TABLE 6 Parts poly(ethylene oxide) I2 I7 22 25 Percent oil retained 10084 6 9 4 2 100 85 8 6 5 4 EXAMPLES 16 to 20 These examples show that awide range of content of poly(ethylene oxide) units in the material ofthe sheath in sheath/core conjugate filaments is effective in conferringantistatic properties of the filaments. A drawn yarn composed offilaments of poly(ethylene terephthalate) of Viscosity Ratio 1.81 wasused as control. Drawn, conjugate filament yarns were prepared fromcopolyesters prepared according to the method described in example 2containing various proportions of poly(ethylene oxide) as the sheathabout a core of poly(ethylene terephthalate) as used for the control.The proportion of the cross-sectional area of the conjugate filamentsoccupied by the core was 85 percent in each case. The antistaticproperties of the derived yarns were tested by knitting into hoselegs,washing free of spin finish, drying, rinsing in aqueous potassiumbromide 1.5 g. per liter), spin drying and tumble drying at 60 C. Thelengthwise electrical resistance of the fabric sample, 7 inches andcomprised of six fabric layers, was measured for each sample. Theresults are given in table 7., in which column 2 shows the parts byweight of poly(ethylene oxide) used in the preparation of 100 parts ofthe copolyester used for the sheath.

TABLE 7 Parts poly- (ethylene oxide) per 100 pts. of copnlymer inElectrical resistance in megohms at relativev humidity Example sheathcomponent 65% The degree of antistatic protection conferred is inverselyrelated to the electrical resistance. These tests show that theantistatic protection increases as the amount of poly(ethylene oxide) inthe sheath increases. It has been established in practical wearer trialsunder normal conditions that a resistance value of about 10 megohms(according to this test) is adequate for normal antistatic protection.

EXAMPLE 21 ment yarn of which 15 percent of the cross-sectonal area wasoccupied by the sheath, according to the method of example 2. Theresultant yarns were tested comparatively in the form of knitted fabricsin respect of antisoiling properties, oil release (test described inexamples 10-l5) and antistatic properties (test described in examples16-20). The results of the tests are given in table 8.

TABLE 8 Poly(ethylene oxide) content of sheath component 5% 12% 20%'Antisoiling test results good good good Oil release test results poorgood good Antistatic test results poor poor good antiantiantistaticstatic static effect effect effect good means there was little soilredeposition.

EXAMPLES 22-25 These examples demonstrate the effectiveness of a rangeof percentages .of cross-sectional area occupied by the sheath of theconjugate filaments of our invention (examples 23-25). A drawn yarncomposed of filaments of poly(ethylene terephthalate) of Viscosity Ratio1.81 was used as control. Drawn, conjugate filament yarns were preparedfrom a copolyester, prepared according to the method described inexample 2 containing a proportion of poly(ethylene oxide) unitsresulting from the use of 18 parts by weight of poly(ethylene oxide) ofaverage molecular weight 5,000 per parts by weight of copolyester, meltspun as the sheath about a core of poly(ethylene terephthalate) as usedfor the control, The percentage of the cross-sectional area of thefilaments occupied by the sheath was varied as required and is given incolumn 2 of table 9. The electrical resistance was measured on fabricsamples as described in respect of examples 16 to 20 after washing withaqueous detergent and also after carrier dyeing followed by reductionclearing and soaping as described in respect of example 2. The resultsare given in table 9. I

TABLE J Electrical resistance, n10 ohms at relative Percentage ofumidlty 65% cross-sectional area occupied After After Example by sheathwashing dyeing etc.

0 10 7 10 7 1.6X10 JX10 1.: (5X10 1x10 33 15x10 3. 5X10 EXAMPLE 26 Adrawn, sheath-core filament yarn of 36 filaments and 4 denier perfilament was prepared according to the method described in example 2,The core was a copolyester of terephthalic and adipic acids withethylene glycol; the molar ratio of adipic acid to terephthalic acid was8:92 and the Viscosity Ratio of the copolymer was 1.81. The sheathcomprised a co(polyethylene terephthalate) of Vlscosity Ratio 1.90 suchas would result from the reaction of 18 parts by weight of poly(ehtyleneoxide) of average molecular weight 5,000 per 100 parts by weight of thefinal copolyester.

Dyeing experiments, carried out in accordance with example 8 and incomparison with the poly(ethylene terephthalate) yarn (sample (i) ofexample 8) showed: (1) that the sheathcore yarn dyed to a deeper shadethan the yarn of sample (i) of example 8, (2) that although some loss ofshade did occur on reduction clearing of the samples, the resultantcolor for the sheath-core yarn was still as deep as, or deeper than, theshade obtained for sample (i) of example 8, (3) that the rub fastnessand other fastness properties were of the same order as those of sample(i) of example 8.

EXAMPLE 27 A series of drawn yarns, nine in all, was prepared accordingto the method of example 2. In each case the yarn was 140 denier and of36 filaments and the filaments consisted of poly(ethylene terephthalate)core of Vlscosity Ratio 1.8 and occupying 85 percent of thecross-sectional area of each filament. The sheath in each case was acopoly(ethylene terephthalate) containing structural units derived frompoly(ehtylene oxide)s of a variety of valves of average molecularweight. The results of the observation of the behavior on unwinding thepackage of spun yarn and the behavior on cold drawing was expressed interms of stickiness and is given in table 10. Column 1 gives the partsby weight of poly(ethylene oxide) reacted to give 100 parts by weight ofthe copoly(ethylene terephthalate). The numbers at the top of columns,2, 3 and 4 are the average molecular weight of the poly(ethylene oxide)on which the sheath copoly(ethylene terephthalate) was based.

TABLE Average molecular weight poly(ethylene oxide) Parts by weight ofpoly(ethylene oxide) 1, 540 4, 000 6,000

25 Very sticky... Sticky Non-sticky.

.... Sticky N onsticky Do.

10. Non-sticky "do Do.

EXAMPLE 28 A sheath-core conjugate yarn of 200 filaments and 1,970 totalspun denier was spun according to the conditions given in example 2. Thecore was poly(ethylene terephthalate of Viscosity Ratio 1.81 andoccupied 85 percent of the total cross-sectional area of the filament.The sheath was a copoly(ethylene terephthalate) of Viscosity Ratio 1.82containing units derived from poly(ethylene oxide) of average molecularweight 5,000 in quantity such as would result from the reaction of 18parts by weight per 100 parts by weight of the final copolyester.

The spun yarn was plied up so as to give a tow of total spun denier250,000. This tow was then drawn on a conventional staple draw-frameusing a pre-draw-frame bath containing a 3 percent by weightconcentration of a processing finish comprising a condensate oflauricacid and 12 mols of ethylene oxide, a steam draw-bath and a draw-ratioof 3.6:1. The drawn tow was mechanically crimped to give 12 crimps perinch,

heat-set at 150 C. for 20 minutes and cut to staple fiber of staplelength 3 inch. 1

The staple fiber was then processed to yarn on conventional worstedmachinery and the yarn was knitted to give a fabric. The fabric wasfound to have good antistatic properties and, when subjected to the testdescribed in example 2, the lengthwise electrical resistance was 2X 10megohms measured at 65 percent relative humidity.

What we claim is:

l. A sheath-core, conjugate, polyester filament wherein the coreconsists of a fiber-forming, linear polyester or copolyester based on asimple glycol, or of a fiber-forming, linear copolyester in themolecular chain of which there are, in addition to units based on asimple glycol, poly(alkylene oxide)-containing units selected from thegroup consisting of oxyethylene and oxypropylene in proportion such aswould result from the reaction of less than 5 parts by weight ofpoly(alkylene oxide) per parts by weight of the final copolyester,

and the sheath consists of a fiber-forming copolyester, or afiber-forming admixture of copolyester, the polyester or copolyesteradmixture of the sheath having structural units containing poly(alkyleneoxide) radicals selected from the group consisting of oxyethylene andoxypropylene the proportion of the structural units containingpoly(alkylene oxide) radicals being such as would result from thereaction of not less than 5 parts and not greater than 60 parts byweight of poly(alkylene oxide) of average molecular weight at least 500per 100 parts by weight of the final copolyester or copolyesteradmixture, and which has been oriented by cold drawing.

2. A sheath-core conjugate filament according to claim 1 wherein theproportion of the structural I units of the copolyester of the corecontaining poly(alkylene oxide) radicals is such as would result from nomore than 3 parts by weight of poly(alkylene oxide) per 100 parts byweight of the copolyester of the core.

3. A sheath-core conjugate filament according to claim 1 wherein thesheath component occupies no less than 5 percent and no more than 40percent of the cross-sectional area of the filament.

4. A sheath-core conjugate filament according to claim 1 wherein thesheath component occupies no less than 7 and no more than 33 percent ofthe cross-sectional area of the filament.

5. A sheath-core conjugate filament according to claim 1 wherein thepoly(alkylene oxide) of average molecular weight at least 500 is ofaverage molecular weight not less than 1,000 and not greater than20,000.

6. A sheath-core conjugate filament according to claim 5 wherein theaverage molecular weight is not greater than 6,000.

7. A sheath-core conjugate filament according to claim 1 wherein theproportion of the structural units of the copolyester or admixedcopolyester of the sheath containing poly(alkylene oxide) radicals issuch as would result from the reaction of not more than 40 parts ofpoly(alkylene oxide) per 100 parts by weight of the final copolyester orcopolyester admixture.

8. A sheath-core conjugate filament according to claim 1 wherein thecore material derives its fiber-forming properties from terephthalatelinkages and the sheath is composed of a copolyester, or has as aconstituent a copolyester, based on terephthalate units.

9. A sheath-core conjugate filament according to claim 8 wherein theterephthalate is ethylene terephthalate or tetramethylene terephthalate.

10. A sheath-core conjugate filament according to claim 1 wherein thecore is composed of poly(ehtylene terephthalate) and the sheath iscomposed of a copolyester of ethylene terephthalate and polyoxyethyleneterephthalate.

11. A process for the preparation ofa conjugate filament by theextrusion in sheath-core relationship of a. a stream of molten,fiber-forming, polyester or copolyester based on a simple glycol orcopolyester in the molecular chain of which there are, in addition tounits based on a simple glycol, poly(alkylene oxide)-containing unitsselected from the group consisting of oxyethylene and oxypropylene inproportion such as would result from the reaction of less than 5 partsby weight of poly(alkylene oxide) per 100 parts by weight of the finalcopolyester, and

b. a stream of copolyester or admixed copolyester of which theproportion of the structural units containing poly(alkylene oxide)radicals selected from the group consisting of oxyethylene andoxypropylene is such as would result from the reaction of not less than5 and not greater than 60 parts by weight of poly(alkylene oxide) ofaverage molecular weight 500 per 100 parts by weight of the finalcopolyester or copolyester admixture, (a) being the core and (b) beingthe sheath, and allowing the composite stream to solidify to form afilament and subsequently orienting by cold drawing.

12. A process for the preparation of a conjugate filament according toclaim 12 wherein the proportion of the structural units of thecopolyester of component (a) containing poly(alkylene oxide) radicals issuch as would result from the reaction of not more than 3 parts byweight of poly(alkylene oxide) per I parts of the component (a).

13. A process for the preparation of a conjugate filament according toclaim 12 wherein component (b) occupies no less than 5 percent and nomore than 40 percent of the crosssectional area of the filament.

14. A process for the preparation of a conjugate filament according toclaim 12 wherein the polly(alkylene oxide) of average molecular weightat least 500 is of average molecular weight not less than 1,000 and notgreater than 20,000.

15. A process for the preparation of a conjugate filament according toclaim 15 wherein the average molecular weight is not greater than 6,000.

16. A process for the preparation of a conjugate filament according toclaim 12 wherein the proportion of the structural units of thecopolyester or admixed copolyester of the sheath containingpoly(alkylene oxide) radicals is such as would result from the reactionof not more than 40 parts by weight of poly(alkylene oxide) per l00parts by weight of the final copolyester or copolyester admixture.

17. A process for the preparation of a conjugate filament according toclaim 12 wherein the core material derives its fiber-forming propertiesfrom terephthalate units and the sheath is composed of a copolyester, orhas as a constituent a copolyester, based on terephthalate units.

18. A process for the preparation of :a conjugate filament according toclaim 16 wherein the terephthalate is ethylene terephthalate ortetramethylene terephthalate.

19. A process according to claim 12 wherein the core material ispoly(ethylene terephthalate) and the sheath material is a copolyester ofethylene terephthalate and polyoxyethylene terephthalate.

20. A textile material composed of, or containing, fibers according toclaim 1.

2. A sheath-core conjugate filament according to claim 1 wherein theproportion of the structural units of the copolyester of the corecontaining poly(alkylene oxide) radicals is such as would result from nomore than 3 parts by weight of poly(alkylene oxide) per 100 parts byweight of the copolyester of the core.
 3. A sheath-core conjugatefilament according to claim 1 wherein the sheath component occupies noless than 5 percent and no more than 40 percent of the cross-sectionalarea of the filament.
 4. A sheath-core conjugate filament according toclaim 1 wherein the sheath component occupies no less than 7 and no morethan 33 percent of the cross-sectional area of the filament.
 5. Asheath-core conjugate filament according to claim 1 wherein thepoly(alkylene oxide) of average molecular weight at least 500 is ofaverage molecular weight not less than 1,000 and not greater than20,000.
 6. A sheath-core conjugate filament according to claim 5 whereinthe average molecular weight is not greater than 6,000.
 7. A sheath-coreconjugate filament according to claim 1 wherein the proportion of thestructural units of the copolyester or admixed copolyester of the sheathcontaining poly(alkylene oxide) radicals is such as would result fromthe reaction of not more than 40 parts of poly(alkylene oxide) per 100parts by weight of the final copolyester or copolyester admixture.
 8. Asheath-core conjugate filament according to claim 1 wherein the corematerial derives its fiber-forming properties from terephthalatelinkages and the sheath is composed of a copolyester, or has as aconstituent a copolyester, based on terephthalate units.
 9. Asheath-core conjugate filament according to claim 8 wherein theterephthalate is ethylene terephthalate or tetramethylene terephthalate.10. A sheath-core conjugate filament according to claim 1 wherein thecore is composed of poly(ethylene terephthalate) and the sheath iscomposed of a copolyester of ethylene terephthalate and polyoxyethyleneterephthalate.
 11. A process for the preparation of a conjugate filamentby the Extrusion in sheath-core relationship of a. a stream of molten,fiber-forming, polyester or copolyester based on a simple glycol orcopolyester in the molecular chain of which there are, in addition tounits based on a simple glycol, poly(alkylene oxide)-containing unitsselected from the group consisting of oxyethylene and oxypropylene inproportion such as would result from the reaction of less than 5 partsby weight of poly(alkylene oxide) per 100 parts by weight of the finalcopolyester, and b. a stream of copolyester or admixed copolyester ofwhich the proportion of the structural units containing poly(alkyleneoxide) radicals selected from the group consisting of oxyethylene andoxypropylene is such as would result from the reaction of not less than5 and not greater than 60 parts by weight of poly(alkylene oxide) ofaverage molecular weight 500 per 100 parts by weight of the finalcopolyester or copolyester admixture, (a) being the core and (b) beingthe sheath, and allowing the composite stream to solidify to form afilament and subsequently orienting by cold drawing.
 12. A process forthe preparation of a conjugate filament according to claim 12 whereinthe proportion of the structural units of the copolyester of component(a) containing poly(alkylene oxide) radicals is such as would resultfrom the reaction of not more than 3 parts by weight of poly(alkyleneoxide) per 100 parts of the component (a).
 13. A process for thepreparation of a conjugate filament according to claim 12 whereincomponent (b) occupies no less than 5 percent and no more than 40percent of the cross-sectional area of the filament.
 14. A process forthe preparation of a conjugate filament according to claim 12 whereinthe poly(alkylene oxide) of average molecular weight at least 500 is ofaverage molecular weight not less than 1,000 and not greater than20,000.
 15. A process for the preparation of a conjugate filamentaccording to claim 15 wherein the average molecular weight is notgreater than 6,000.
 16. A process for the preparation of a conjugatefilament according to claim 12 wherein the proportion of the structuralunits of the copolyester or admixed copolyester of the sheath containingpoly(alkylene oxide) radicals is such as would result from the reactionof not more than 40 parts by weight of poly(alkylene oxide) per 100parts by weight of the final copolyester or copolyester admixture.
 17. Aprocess for the preparation of a conjugate filament according to claim12 wherein the core material derives its fiber-forming properties fromterephthalate units and the sheath is composed of a copolyester, or hasas a constituent a copolyester, based on terephthalate units.
 18. Aprocess for the preparation of a conjugate filament according to claim16 wherein the terephthalate is ethylene terephthalate or tetramethyleneterephthalate.
 19. A process according to claim 12 wherein the corematerial is poly(ethylene terephthalate) and the sheath material is acopolyester of ethylene terephthalate and polyoxyethylene terephthalate.20. A textile material composed of, or containing, fibers according toclaim 1.